Optical read/write devices, as with many complex optical devices, commonly include a plurality of different optical elements along an optical path which can affect characteristics of the beam which travels along the optical path. For example, depending on the design and configuration of the device, the optical path may include one or more lenses or other refractive elements, holograms, gratings or other diffractive elements, flat or shaped mirrors and the like. Each element in an optical path can change one or more optical characteristics of the beam and/or may influence the manner in which other, “downstream” optical elements influence the beam. The resultant multiple optical characteristics and interactions of the various elements often results in a optical system which is difficult, time-consuming and expensive to design, test, fabricate and the like. For this reason, creating multiple different optical path designs, or making modifications in an optical path design is not done lightly or easily, especially for complex optical devices such as an optical read/write device.
In addition to the cost of designing complex systems, there are also costs associated with maintaining stocks or inventories of components needed to fabricate two or more different systems, costs associated with designing devices and/or training personnel for assembling two or more different devices, maintaining or repairing two or more different systems and the like.
Previous approaches to optical read/write devices have typically involved a choice between either foregoing the anticipated or potential advantages that might arise from a new or modified design (in order to avoid certain costs), or undertaking the costs associated with a new or modified design in hopes that the costs for the new or modified design will be justified by technical, marketing, manufacturing or other advantages arising from the new or modified design. Unfortunately, because of the complexity of optics in general and interactions between optical components, it is often infeasible to accurately determine the cost for a new or modified design, or the advantages associated with a proposed new or modified design, in advance. Accordingly, it would be useful to provide a method, system and apparatus which can provide for one or more changes in the optical design, such as adding or changing a first element along an optical path of a read/write device (or other optical device) while reducing or substantially eliminating the changes in at least some optical parameters or characteristics of other optical elements in the optical path (or how such other elements affect the beam). By reducing or eliminating influences on, or changes in operation of other optical elements (for at least some optical parameters) it is possible to reduce or avoid the need for redesigning other optical elements in the system, as a consequence of changing, adding or redesigning one (or a group) of optical elements, and thus reducing the overall cost associated with a design change or modification. By reducing the cost of system design change or modification, as well as by reducing the uncertainty in estimating the cost (since a smaller number of components need to be changed, modified or added) it becomes more feasible to develop multiple or modified optical path designs which can be useful both during product or system development (e.g., permitting parallel development of two or more different options for a design) and/or for accommodating two or more different potential component vendors, sources, component characteristics and the like.
In one situation, it may be desirable to perform parallel development on a design which includes a beamshaper and second design which does not include a beamshaper. For example, in a system which provides laser (or other) light to an objective lens (as described below) for addressing an optical disk or similar medium, it may be possible to achieve a desired light intensity profile at the objective lens by “overfilling” the lens (and “spilling” the relatively lower-intensity light at the perimeter of the beam). On the other hand, this technique can result in spilling or wasting a substantial amount of the total laser (or other light source) output, requiring a higher-power source in order to achieve desired intensity (or intensity profile) as delivered to the medium. Higher-power laser devices or other sources may be not only more expensive but may lead to certain secondary costs or effects such as costs of a larger power supply and/or a need for dissipating a greater amount of heat. Accordingly, it may be useful to include a beamshaper which can assist in delivering the desired intensity (or intensity profile) to an objective lens, without the need for overfilling the lens, e.g., by “circularizing” or otherwise changing the beam cross-sectional shape and/or by changing the beam (cross-sectional) intensity profile. In many situations, it may be infeasible to know, in advance, which option is preferable. However, it may be economically infeasible to create two or more completely different optical path designs (i.e., modifying all or substantially all optical elements in the optical path), especially given the complex interaction between optical components, even though only one of the designs is likely to be ultimately used. Accordingly, it would be useful to provide a method, system or apparatus for an optical read/write device (or other optical device) in which the operation or nature of a plurality of elements along the path, and/or the magnitude or nature of at least some optical parameters of the beam, is substantially unchanged regardless of whether the optical path includes a beamshaper or does not include beamshaper. In this way it would be possible to, e.g., design an optical path which did not include a beamshaper, and yet have the ability to insert a beamshaper, if that option is ultimately desired, while reducing or eliminating the need for redesigning other (non-beamshaper) elements or aspects of the optical path.
The usefulness and/or need for a beamshaper in an optical path of the type described above can be, at least in part, dependent on the characteristics of the laser or light source. Not uncommonly, batches of lasers, as delivered, may have a substantial amount of variability in the characteristics of the output light. Thus, in a manufacturing context, even within a single batch or delivery of laser devices, there may be some which operate best in a system without a beamshaper and others which operate best with (or require the use of) a beamshaper. In previous approaches, typically it was necessary to either undertake the costs of completely designing or modifying the optical path, to produce two completely different designs (i.e., changing or modifying all or substantially all components in the optical path), one for use with lasers that require a beamshaper, and another for use with remaining lasers, or to select one of the designs with the knowledge that a number of lasers (or other light sources) in any order or batch will need to be discarded or otherwise disposed of. Accordingly, it would be useful to provide an optical system which is substantially the same in all or nearly all non-beamshaper components, regardless of whether a beamshaper is present, or not. In this way, it is feasible to use substantially all lasers (or other light sources) in an order or batch, but without incurring costs needed for developing two completely different optical paths.
A number of optical reader/writer devices, including, for example, relatively large devices such as audio compact disk (CD) players in a typical home stereo system, present relatively little concern with power management or power budgets (typically having access to AC line level power or the like). As a result, in many such systems, it is feasible to provide an optical design which is relatively inefficient of optical power (such as by substantially overfilling lenses and the like, e.g. to accommodate noncircularity of laser sources). In contrast, devices such as those described in application Ser. No. 09/315,398, supra and or 60/140,633 intended to be lightweight and portable, generally must operate with a limited power budget (and also have a more limited ability to dissipate heat, compared with larger systems). Accordingly, it would be useful to provide an optical head apparatus, system and method which can achieve the desired optical quality (e.g. accommodating noncircularity or other optical features) while avoiding, as needed or useful, undue energy inefficiency and/or unnecessary heat generation (e.g. arising from substantial overfilling of lenses or other optical inefficiencies which in turn require higher optical power and hence higher electrical power lasers which dissipate more heat).